Every team has several weaknesses. Barcelona's performance is erratic. In La Liga, they could not occupy the top spot in the table. Real Madrid is playing very well it is true. However, the attacking side of this team is quite weak. Real Madrid are reliant on their midfielders. Manchester City's squad looks very strong but the City's midfield is quite weak without De Bruyne. And because of this, City's performance is also a bit slow compared to the previous season. All teams have some weaknesses. This is why it is difficult to predict which team will win the Champions League title this season. Despite Barcelona's erratic performance, this team will also be considered favorites for the Champions League title. Because they have an excellent squad.
I don't think that Barcelona are favorites in the UCL this season, I think it's quite impossible after seeing Barcelona's performance which is not that good and they are even experiencing a lot of problems, in La Liga alone the Barcelona team is having a really hard time, especially in the UCL but luckily because Barcelona joined the team The team is weaker in the group phase, but in the know-out round, I don't think there is a big possibility for Barcelona when facing a stronger top European team.
Barcelona did perform well in the Champions League but that does not mean Barcelona is the favorite in the Champions League because Barcelona it is facing a team that is not too difficult for to faced and Barcelona can lead Group H at the moment.
I thinks Barcelona still has a lot to learn because the competition in the UCL is very tight especially since they just suffered a defeat against Real Madrid so I don't think Barcelona has a chance to trophy in the Champions League this season.
in my opinion the strong candidates to win the title this season are Manchester City, Bayern Munich and Real Madrid.